1. Field of the Invention
The invention is generally related to the area of data storage devices. Particularly, the present invention is related to techniques for building up a flash-based solid state disk (SSD) with individual flash memory cards.
2. The Background of Related Art
A traditional hard disk device, sometimes also referred to as Hard Disk Drive (HDDs) has been around for many years. It records data by magnetizing a magnetic material in a pattern that represents the data. Data is read out by detecting the magnetization of the material. A typical HDD design includes a spindle which holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually glass or aluminum, and are coated with a thin layer of magnetic material. Despite these fine mechanical moving parts, the hard disks are almost every where that requires a large storage capacity and read/write speed.
Flash memory is non-volatile, which means that it does not need power to maintain the information stored in the flash memory chip. In addition, flash memory offers fast read access times and better kinetic shock resistance than the hard disks. However, the high price of the flash memory in the past has prevented it from making significant inroads into large storage devices.
With the prices of flash memory continuing to decline dramatically over the recent years while the capacities continue to increase, flash-based data storage device, also referred to as Solid-state drive (or SSD) has gained tremendous attention recently, due to the fact that they will provide relatively high storage capacities, as well as a very high degree of reliability and shock-resistance, especially for mobile or portable applications.
The capacity of the flash memory increases almost every month with the new technologies in place. A flash SSD designed upon the current available flash memories would soon become obsolete when flash memories with much higher capacity become available. For example, the current popular flash memories come in capacity of 1 GByte and 2 Gbyte. A typical SSD would employ 4 or 8 of these memories, resulting in 4 Gbytes to 16 Gbyte in storage capacity. When the flash memories are increased to the capacity of 16 GByte or 32 Gbyte, an SSD could be easily built with a capacity of 16 Gbytes to 256 Gbytes, without much difficulty.
In the past, computer users have kept changing their hard disks for the sake of storage capacity. With more and more media files captured, the users soon notice that their current hard disks are nearly full and start to look for hard disks with larger capacity. Because of the superior features in flash SSD, computer users may already start to adopt the flash SSD despite relatively small capacity of current flash SSD. When the flash memories with large capacity come to reality, flash SSD of large capacity will become available. Solutions of not changing a disk but still increasing the storage capacity will be certainly welcome Likewise, techniques of minimizing the costs of building up flash SSD are very much needed.